Crevice Corrosion Behavior of Stainless Steels in a Flue Gas Desulfurization Environment

In this study, cyclic potentiodynamic polarization, potentiodynamic–potentiostatic–potentiodynamic (PD–PS–PD) impedance, and semiconductor performance tests, combined with SEM/energy spectroscopy and XPS detection were used to systematically study the crevice corrosion behavior of SS904L, SS2205, SS2507, and SS254SMO stainless steels with synthetic crevice electrodes in simulated mixture solution of NaCl (10 g/L) and Na2SO4 (5.7 g/L) at 60 °C and pH = 3.5. The results showed that the corrosion behavior among the four stainless steels was most severe at the crevice mouth position, and the SS2507 formed passive films with better stability. Through the discussion of four stainless steels crevice corrosion mechanisms, the crevice geometry restricts the diffusion of metal ions and produces an autocatalytic effect to promote the development of crevice corrosion. Cr, Mo and N have a synergistic effect that improves resistance to crevice corrosion. The crevice corrosion resistance of the four stainless steels decreased in order of SS2507 > SS254SMO > SS904L > SS2205.